The purpose of this research is to describe how perinatal steroid hormones influence the development of male and female reproductive processes. Androgen or its metabolic products can determine the age of cessation of ovulation and behavioral receptivity. How ovarian secretions, hormonal conditions prevalent during pregnancy and lactation, depletion of the putative neurotransmitters: noradrenaline, dopamine and serotonin, nutrition, photoperiods and other conditions influence age-related and hormonally induced time-dependent changes in reproductive competence are being evaluated. The action of androgen, estrogen and nonaromatizable androgens on development of sexual behavior and gonadotropin function are being compared. Neural areas that might be modified by perinatal hormones are being studied. LH-RH pathways and cell bodies, identified by an immunocytochemical method, are being compared in males and females throughout their life span. The interaction of perinatal hormones and neural systems with the LH-RH system is under investigation. An attempt is being made to understand the synergistic action of progesterone in inducing estrous behaviors in estrogen-primed male and female animals. BIBLIOGRAPHIC REFERECES: King, J.C., Gerall, A.A., Fishback, J.B., & Elkind, K.E. Growth hormone release inhibiting hormone (GH-RIH) pathway of the rat hypothalamus revealed by the unlabeled antibody peroxidase-antiperoxidase method. Cell Tissue Research, 1975, 160, 423-430. Gerall, A.A. & Thiel, A.R. Effects of perinatal gonadal secretions on parameters of receptivity and weight gain in hamsters. Journal of Comparative and Physiological Psychology, 1975, 89, 580-589.